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USSD CBS Walkthroughs and Assignments

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USSD CBS Walkthroughs and Assignments

Overview

This section combines guided walkthroughs and hands-on assignments to help learners progressively build a USSD-based Community-Based Surveillance (CBS) system using Africa’s Talking, Flask or Express, and ngrok.

Each walkthrough introduces new technical concepts, immediately followed by an assignment that reinforces learning through practical implementation.

Learning Flow

The module follows a learn–build–test approach:

  1. Understand USSD concepts and session flow
  2. Implement features step by step
  3. Test locally using ngrok and the USSD simulator
  4. Apply concepts to real CBS use cases

Walkthrough 1: USSD Fundamentals and Session Flow

Concepts Covered

  • What USSD is and how it works
  • Session-based communication
  • Role of sessionId
  • Use of CON and END
  • Africa’s Talking USSD request lifecycle

Walkthrough

  • Inspect the USSD HTTP POST payload
  • Identify text == "" as session start
  • Send a simple menu response
  • Terminate a session correctly

Assignment 1: Basic USSD Menu

Task:
Create a USSD endpoint that:

  • Displays a menu on first request
  • Continues and ends sessions correctly

Outcome:
Learner understands basic USSD interaction and response rules.

Walkthrough 2: Multi-Level Menu Navigation

Concepts Covered

  • Understanding the text field
  • *-concatenated user input
  • Menu depth and navigation logic
  • Stateless USSD design

Walkthrough

  • Trace text values ("1", "1*2", "1*2*1")
  • Map input paths to menus
  • Implement branching logic

Assignment 2: Hierarchical Menus

Task:
Build a two-level USSD menu with:

  • Valid input handling
  • Invalid input fallback

Outcome:
Learner can design and control multi-step USSD flows.

Walkthrough 3: Local Development with ngrok

Concepts Covered

  • Why public HTTPS endpoints are required
  • ngrok tunneling architecture
  • Debugging USSD callbacks

Walkthrough

  • Run the local server
  • Expose it using ngrok
  • Configure Africa’s Talking callback URL
  • Inspect requests via ngrok dashboard

Assignment 3: ngrok Integration

Task:
Expose your local USSD app with ngrok and test it using the Africa’s Talking simulator.

Outcome:
Learner can develop and debug USSD apps locally.

Walkthrough 4: Designing CBS USSD Menus

Concepts Covered

  • CBS reporting requirements
  • User-centered USSD menu design
  • Avoiding deep navigation
  • Telco rendering constraints

Walkthrough

  • Design a CBS menu for:
    • Illness reporting
    • Death reporting
    • Animal health events
  • Validate menu clarity and flow

Assignment 4: CBS Menu Design

Task:
Design and document a CBS USSD menu suitable for community use.

Outcome:
Learner understands how to translate public health needs into USSD menus.

Walkthrough 5: Implementing CBS Reporting Logic

Concepts Covered

  • Mapping USSD input to CBS events
  • Capturing and confirming reports
  • Ending sessions with acknowledgment

Walkthrough

  • Implement illness and death reporting flows
  • Simulate report submission
  • Return confirmation messages

Assignment 5: CBS Report Capture

Task:
Implement backend logic to capture CBS reports and acknowledge users.

Outcome:
Learner can build functional CBS reporting workflows.

Walkthrough 6: Error Handling and User Experience

Concepts Covered

  • Graceful handling of invalid input
  • Preventing session crashes
  • User-friendly termination messages

Walkthrough

  • Simulate incorrect inputs
  • Implement fallback responses
  • Ensure session stability

Assignment 6: Robustness Improvements

Task:
Add error handling and improve UX across all menus.

Outcome:
Learner builds resilient USSD applications.

Walkthrough 7: Performance and Best Practices

Concepts Covered

  • USSD timing constraints
  • Logging and monitoring
  • Stateless vs cached session design

Walkthrough

  • Measure response times
  • Add basic logging
  • Identify production risks

Assignment 7: Optimization

Task:
Optimize your USSD application for speed, clarity, and maintainability.

Outcome:
Learner prepares USSD systems for real-world deployment.

Final Project: CBS USSD Mini System

Objective

Integrate all concepts into a working CBS USSD prototype.

Requirements

  • Multi-level CBS menu
  • Illness and death reporting
  • ngrok-enabled testing
  • Simulator-tested flows

Deliverables

  • Source code
  • Menu flow diagram
  • Short technical documentation

Outcome

Learner demonstrates full competency in building a USSD-based CBS system.

Expected Competencies After Completion

By completing these walkthroughs and assignments, learners will be able to:

  • Build end-to-end USSD applications
  • Integrate Africa’s Talking USSD APIs
  • Test and debug locally using ngrok
  • Design and implement CBS reporting systems
  • Apply USSD best practices for public health solutions

Conclusion

This combined walkthrough-and-assignment approach ensures learners not only understand USSD concepts, but can apply them to real Community-Based Surveillance challenges, resulting in practical, deployable solutions suitable for real-world environments.